There is a need in the aquarium field for means of using soil in aquariums for growing certain rooted aquatic plants. Prior to the present invention soil was placed in a small pot; the pot was carefully lowered into an aquarium with some sand or gravel on top of the soil to keep the soil from dispersing (by flotation) in the water of the aquarium; and then the pot was buried under gravel in the aquarium. Fish in the aquarium would inevitably disturb the gravel covering the pot, and the soil thereunder would disseminate throughout much of the aquarium.
As confirmed, e.g., by Gerhard Brunner's "Aquarium Plants", T.F.H. Publications, Inc., Ltd., 1973, there is material interaction between fish and plants in an aquarium; the presence of the fish has a profound effect on the plants, and vice versa. There is an interdependency.